Antibodies conjugated with viral antigens elicit a cytotoxic T cell response against primary CLL ex vivo

Chronic lymphocytic leukemia (CLL) is the most frequent type of B cell leukemia in adults. Treatment options against this incurable disease have continually been expanding with strategies using specific antibodies, inhibitors and individualized adaptive immunotherapy. However, none of these approaches is curative and devoid of adverse effects. In this preclinical ex vivo study, a novel therapeutic approach has been developed that uses B cell-specific antibodies coupled with antigens (antigen-armed antibodies, AgAbs) derived from the Epstein-Barr virus (EBV). The breadth of the immunogenic epitope repertoire within the coupled antigen is a critical factor for the immune response amplitude as it determines the potential number and diversity of memory T cell clones that can be reactivated. Along this line, a strongly immunogenic latent EBV antigen named EBNA3C was fragmented into large segments and conjugated to the antibody vehicles. Application of these antibody conjugates to leukocytes isolated from treatment-naïve CLL patients led to an efficient expansion of CD4+ T cells that recognized EBNA3C in all tested cases. Moreover, CLL cells pulsed with EBNA3C-AgAbs induced specific responses of these T cells with widely varying intensities across the patient population. Interestingly, a large proportion of the EBV-specific T cells consisted of highly efficient cytotoxic T lymphocytes (CTLs) that eliminated CLL cells loaded with EBNA3C through the granzyme B (GrB)/perforin-mediated pathway. The encouraging results from this study demonstrate the potential of AgAbs to redirect endogenous CD4+ CTLs against CLL cells loaded with EBV antigens in a high percentage of patients, and warrants the inception of clinical trials

Immunogenic particles with a broad antigenic spectrum stimulate cytolytic T cells and offer increased protection against EBV infection ex vivo and in mice.

The ubiquitous Epstein-Barr virus (EBV) is the primary cause of infectious mononucleosis and is etiologically linked to the development of several malignancies and autoimmune diseases. EBV has a multifaceted life cycle that comprises virus lytic replication and latency programs. Considering EBV infection holistically, we rationalized that prophylactic EBV vaccines should ideally prime the immune system against lytic and latent proteins. To this end, we generated highly immunogenic particles that contain antigens from both these cycles. In addition to stimulating EBV-specific T cells that recognize lytic or latent proteins, we show that the immunogenic particles enable the ex vivo expansion of cytolytic EBV-specific T cells that efficiently control EBV-infected B cells, preventing their outgrowth. Lastly, we show that immunogenic particles containing the latent protein EBNA1 afford significant protection against wild-type EBV in a humanized mouse model. Vaccines that include antigens which predominate throughout the EBV life cycle are likely to enhance their ability to protect against EBV infection